This invention relates generally to thermosiphon or heat pipe devices for removing from a heat generating system or reservoir large quantities of heat by vaporization of a liquid at one end of the device and condensation of the vapor so produced at another end. More specifically, this invention relates to an improved thermosiphon or heat pipe device utilizing a diamagnetic or paramagnetic fluid which may be circulated through the device by the imposition of a magnetic field gradient.
The use of a thermosiphon for the extraction of large quantities of heat from a heat generating system provides certain well known advantages over cooling systems utilizing single phase heat transfer media, particularly as regards its great capacity for heat extraction over a relatively small temperature differential between heat source and heat sink. However, thermosiphons require for their operation an externally applied gravitational or rotating inertial force field to effect separation of the gaseous phase from liquid phase of the heat transfer medium. One conventional heat pipe configuration utilizes a wick to separate the phases and to return the liquid phase to the hot (evaporator) end of the heat pipe through the wick by capillary action. One wickless configuration employs an internally tapered tube spinning about its axis whereby centrifugal force returns the condensed liquid phase of the heat transfer medium to the larger diameter evaporator end of the device.
Conventional thermosiphon configurations therefore are limited in their use in zero-gravity or other orientation insensitive environments, while conventional wick configured heat pipes are limited in their use in a gravity environment.
The present invention comprises a two-phase heat pipe utilizing an artificial body force field analogous to the gravitational field in which all the fluid convective phenomena observed in the latter can occur with controlled intensity and independently of orientation. This invention has significant advantage over prior art devices in that it generates its own body force field induced in paramagnetic or diamagnetic working fluids by magnetic field gradients. By proper choice of magnetically susceptible working fluids, the invention may be applicable within various temperature ranges from cryogenic through ambient and elevated temperatures. Permanent magnet or electromagnetic means may be used for producing the magnetic field gradients for pumping a magnetically susceptible working fluid such as certain organic liquids, such as benzene, saturated and unsaturated hydrocarbons of the methane, ethylene, and acetylene series of homologous organic compounds, the halocarbons, rare gases, and hydrides. As a result of heat addition at the evaporator end of the device some of the magnetically susceptible liquid is vaporized producing an imbalance in hydrostatic pressure at one extremity of parallel liquid and vapor filled columns of one embodiment, thereby inducing gross circulation of liquid from the denser to the more rarefied fluid mixture column. At the other extremity, the parallel columns communicate through a passage, which allows vapor to contact a condenser located near the liquid column where the vapor condenses and returns to the liquid column. The magnetic gradient may be produced by conductor coils surrounding the heat pipe wherein the density of windings varies over the region occupied by the liquid and vapor columns. The heat pipe may be constructed of suitable non-ferromagnetic material such as aluminum, glass, copper and brass.
The magnetic body force field of this invention which acts upon the magnetically susceptible working liquid within the heat pipe may be made to be substantially greater than the gravitational force and provides a means of establishing an intrinsic body force field that remains virtually undisturbed by the variable g-forces induced by an accelerating coordinate system. This invention will allow the high intensity heat transfer mechanisms of boiling and condensation to be applied to the task of recouping on-board waste heat to power environmental control systems and possibly other subsystems and to render such heat power cycles insensitive to accelerations. The invention may be used for cryogenic heat pipes associated with optical sensor cooling, in heat pipes based on liquid metals and fused salts, and in cooling applications for special purpose high power systems and magneto-hydrodynamic generators.
The invention described herein, therefore, provides an improved heat pipe using a diamagnetic or paramagnetic fluid in a body force field produced by an imposed magnetic field gradient, wherein the field gradient may be produced by an electromagnet, comprising a graduated winding density, or permanent magnets having a field gradient such as would be produced by conical configuration of permanent super magnets such as samarium cobalt; permanent and superconducting magnets may be used to minimize energy consumption of the heat pipe device of this invention.
It is, therefore, an object of this invention to provide an improved thermosiphon or heat pipe device.
It is a further object of this invention to provide a heat pipe operable in various temperature regimes.
It is still a further object of this invention to provide a heat pipe operable in zero-gravity or other orientation insensitive environments.
It is a further object of this invention to provide a heat pipe operable in an environment wherein gravitational forces may need to be overcome.
These and other objects of the invention will become apparent as the description thereof proceeds.